One of conventional effective CO2 reduction measures in global warning countermeasures is to install idle reduction systems into motor vehicles. Such an idle reduction system installed in a motor vehicle is designed to shut off fuel injection into an internal combustion engine when the motor vehicle is temporarily stopped at, for example, a light or by a traffic jam, thus automatically stopping the internal combustion engine, referred to simply as “engine”.
After the stop of the engine, the idle reduction system is designed to automatically activate a starter when an engine restart request occurs in response to a driver's operation to start the motor vehicle, thus restarting the engine; the driver's operation is, for example, a brake releasing operation, a shift operation of a shift lever to a drive range, or the like. These idle reduction systems reduce the idling state of motor vehicles, resulting in reducing in fuel cost and in exhaust emission.
Conventional starters normally include a solenoid switch. The solenoid switch is designed to magnetically pull a plunger into a solenoid to thereby slidably shift a pinion along an output shaft coupled to a motor so that the pinion is engaged with a ring gear of the engine. The pull-in stroke of the plunger allows a motor-energizing switch (relay) to be turned on so that the pinion is rotated by the motor together with the ring gear, thus cranking the engine. One of the conventional starters is disclosed in Japanese Patent Application Publication NO. H05-180130.
In these starters, in order to smoothly engage the pinion with the ring gear, a large amount of grease as lubricants is put onto slidably contact portions of their parts for shifting the pinion.
However, a higher viscosity of the grease increases the resistance between the slidably contact portions in low-temperature environments, such as cold regions. The increase in the resistance between the slidably contact portions of a starter increases time taken to engage the pinion with the ring gear. In other words, starters have different time taken to engage their pinions with their ring gears from one another depending on their use environments. The time taken to engage the pinion with the ring gear in a starter will be referred to as “pinion-engagement time” hereinafter.
In a motor vehicle equipped with the idle reduction system, frequent engine-automatic stop and restart increases the frequency in use of the starter, resulting in increasing the number of engagements between the pinion and ring gear. For this reason, wear of each of the pinion and ring gear may increase, resulting in change of the friction coefficient of the gear surfaces and change of the shift stroke of the pinion.
Specifically, there is a variation in the pinion-engagement time of starters due to the use environments of the starters. In addition, there is a variation in the pinion-engagement time of starters due to their types.
The variations may cause a variation in the timing when the shifted pinion abuts on the ring gear and a variation in the timing when the pinion is rotated together with the ring gear by torque transferred from the motor among starters due to their use environments and/or their types. The former timing will be referred to as “pinion abutment timing”, and the latter timing will be referred to as “pinion rotation timing” hereinafter.
For this reason, conventional starters are each designed to ensure a predetermined temporal difference between the pinion abutment timing and the pinion rotation timing so as to prevent the pinion abutment timing from being earlier than the pinion rotation timing. In other words, conventional starters are each designed to ensure a predetermined temporal difference between the pinion abutment timing and the pinion rotation timing so as to prevent the rotation of the motor together with the ring gear before the abutment of the pinion onto the ring gear. The temporal difference will be referred to as “safety time” hereinafter.